Estimates of micro-, nano-, and picoplankton contributions to particle export in the northeast Pacific

[摘要] The contributions of micro-, nano-, and picoplankton to particle export wereestimated from measurements of size-fractionated particulate ²³⁴Th,organic carbon, and phytoplankton indicator pigments obtained during fivecruises between 2010 and 2012 along Line P in the subarctic northeast PacificOcean. Sinking fluxes of particulate organic carbon (POC) and indicatorpigments were calculated from ²³⁴Th–²³⁸U disequilibria and, duringtwo cruises, measured by a sediment trap at Ocean Station Papa. POC fluxes at100 m ranged from 0.65 to 7.95 mmol m⁻² d⁻¹, similar in magnitudeto previous results at Line P. Microplankton pigments dominate indicatorpigment fluxes (averaging 69 ± 19% of total pigment flux), whilenanoplankton pigments comprised the majority of pigment standing stocks(averaging 64 ± 23% of total pigment standing stocks). Indicatorpigment loss rates (the ratio of pigment export flux to pigment standingstocks) point to preferential export of larger microplankton relative tosmaller nano- and picoplankton. However, indicator pigments do notquantitatively trace particle export resulting from zooplankton grazing,which may be an important pathway for the export of small phytoplankton.These results have important implications for understanding the magnitude andmechanisms controlling the biological pump at Line P in particular, and moregenerally in oligotrophic gyres and high-nutrient, low-chlorophyll (HNLC) regionswhere small phytoplankton represent a major component of the autotrophiccommunity.

[学科分类] 地球化学与岩石